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An apple a day keeps the doctor away

We’ve all heard the saying that an apple a day keeps the doctor away, probably beginning way back when you were a youngster and your parents were trying to get you to eat some fresh food. Is there any truth in it?

A study in the 30th March 2015 edition of the Journal of the American Medical Association attempted to address the question by conducting a cross-sectional study of a nationally representative sample of the noninstitutionalized US adult population.  A total of 8728 adults 18 years and older from the 2007-2008 and 2009-2010 National Health and Nutrition Examination Survey completed a 24-hour dietary recall questionnaire and reported that the quantity of food they ate was reflective of their usual daily diet.  Daily apple eaters were taken as those who consumed the equivalent of at least one small apple (about 150g) daily. 

The primary outcome measure was success at “keeping the doctor away,” measured as no more than one visit to a physician during the past year.  Secondary outcomes included successful avoidance of other health care services, ie no overnight hospital stays, visits to a mental health professional, or prescription medications. Of 8399 eligible study participants who completed the questionnaire, there were 753 apple eaters (9.0%) and 7646 non-apple eaters (91.0%). Without considering any other contributing factors, the apple eaters were more likely to keep the doctor (and prescription medications) away, but after adjusting for sociodemographic and health-related characteristics, this association was no longer seen. There were also no differences between the two groups in overnight hospital stay or mental health visits, but the apple eaters were marginally more successful at avoiding prescription medications. The authors concluded their data did not support the  ‘apple a day keeps the doctor away’ belief, but did note that the small fraction of US apple eaters appear to use fewer prescription medications.

Questionnaire studies are always subject to the reliability of information gathered.  In this case, how well does a 24hour snap-shot represent what someone consumes on a yearly basis, and do participants report or remember accurately.  Nevertheless, such information is still better than the unfounded cultural beliefs of the past. The small proportion of US adults who regularly eat apples is interesting, but this ties in with another 2015 study where it was found that more than 60% of the daily calorie intake in US households came from processed foods.  If taken literally, the advice regarding apples would be expected to produce a negative result in any properly conducted study, as no single food, no matter how favoured, could hope to provide all the necessary nutritional components to ensure long-term well-being.  If, however, it is more loosely interpreted to simply mean ‘eat more fruit and vegetables’, then it’s excellent.

Are organically produced apples healthier than those produced conventionally?

Ever since mankind moved from a hunter-gatherer nomadic lifestyle eating what was available, to more settled communities when plants were grown and animals domesticated, more reliable sources of food became possible. Thereafter, how these foods were selected, bred and managed began to affect their nutritional contribution to the diet. Primitive agriculture was organic by necessity, and although yields slightly improved over millennia with selection of chance superior varieties and trial and error improvements in cultivation, yields were still low until the industrial revolution. This ushered in synthetic agrochemicals, and modern science began to speed up the introduction of better performing varieties and management techniques. For the first time in history, the more advanced societies were then able to produce plentiful and very affordable food. This approach was eagerly embraced and food production continued to grow seemingly without limit over much of the last century, that is until adverse reports began describing soil degradation, pesticide resistance, contamination of water systems, health effects on humans and animals, reduction in biodiversity, carbon dioxide emissions etc.

Since then, public concerns and scientific reports have led to government agencies imposing increasingly strict controls on practices and chemicals, so that agricultural management today has been forced to move back somewhat in the direction of organic farming, while still making use of the best of both practices where possible. In contrast, the certified organic philosophy is to disallow all forms of synthetic fertilisers and pesticides, along with other restraints. It’s an extreme position deriving from pre-industrial times and doesn’t exploit the opportunities of finding a balance between earlier practices and the demonstrated benefits (consistent with minimising risks) afforded by scientific advances. A middle road, called integrated farming, has been adopted by many farmers and regions worldwide as the wisest approach given the ever-increasing need to feed an expanding world population and decrease the proportion who are undernourished. Global food demand is predicted to double by 2050 and we’ve already converted the most arable lands to agriculture, so production systems will have to be efficient, sustainable, healthy, safe and open to new research findings if we’re going to have any hope of getting there.

Demand for organically-produced foods in the US has been increasing by an average of 20% a year since the 1990s. While still only 2% of the total market in 2006, sales nevertheless amounted to US$13.8 billion in that year and seem likely to continue growing rapidly. Fresh fruit and vegetables are the biggest segment of the US organic food market, with vegetables accounting for most. Apples and tomatoes lead their respective lists, and women are more likely to buy organic than men. There has been similar rapid growth in Australia with retail sales of AU$28m in 1990 and $250m in 2003. Community surveys reveal that continuing growth in organic foods has come from concerns and beliefs regarding conventional foods, and they can vary greatly between individuals. They include cultural and religious beliefs, unsustainable use of finite resources in conventional production systems, ecological damage from heavy artificial fertiliser use on water systems, global warming from fertiliser manufacture, health issues with synthetic pesticide and herbicide use by consumers and farmers, pesticide damage to fauna, flora and soil microbiota, soil erosion and degradation, pathogen resistance development, a belief that nutrition and taste are better with organic products, and a recognition of the adverse link between dietary habits relying unduly on modern fast and extensively processed foods and health and well-being. These adherents are prepared to pay an increased price (10-50% average but sometimes >100%) for the organic product instead of the invariably cheaper one produced conventionally. This price premium offsets the generally (but not always) lower yields and higher costs and labour associated with organic foods, and helps to encourage farmers to go organic to seek out a marketing niche for their produce.

However the public has considerable mistrust of non-certified food labelled as organic because of marketers seeking to gain the price premium on the cheap. Surveys show that total organic food demand is predominantly driven by the strongly committed few who eat organic most of the time, topped up by a much larger number who only eat organic occasionally. Many of the above issues concerning conventional farming systems are outside the scope of our fruit club, and more complete discussion is best left to other more suitable forums. Here we’ll concentrate mainly on the relative nutritional merits of organic and conventionally produced fruit, which obviously feeds into health, and make only passing comments on some of the other issues. Ideally, nutritional comparisons should be led by properly conducted evidence-based research rather than beliefs based on tradition, hearsay, religious conviction, mis-information and halftruths, faddism etc.

Just considering fruit, there have been hundreds of studies addressing the issue given its importance, eg data from the 2013 Global Burden of Disease study showed that the leading behavioural risk factor for disability-adjusted life years in England was suboptimal diet, now ahead of tobacco. Generally it’s found that the macronutrients, vitamins, minerals and fibre vary little between organic and conventional, and differences are not consistent, with some studies showing conventional higher than organic and others the reverse or no difference. Either way, these minor differences are dwarfed by differences between cultivars, growing season, level of fertilisation, precipitation, variation in harvest times etc which can often be two-fold or more. More recently the question of relative nutritional qualities has moved on to the phytochemicals. These are plant secondary metabolites produced in defence against environmental stresses such as wounding, insects, microbial pathogens, foraging animals and radiation. The hypothesis is that organic plants, without the benefit of synthetic pesticides and herbicides are under greater stress and will produce more, and these substances are thought to be very strong players in chronic disease prevention. However this proposal is not all one-sided, as defence phytochemicals also include unhealthy chemicals like astringent tannins, cyanogenic compounds, alkaloids and anti-nutrients which also may be induced. Many of these would not be allowed if subjected to the same degree of scrutiny and testing placed on pesticides. Also with organic growing where there is higher pest load, particularly with more humid conditions, it may be necessary to spray a dozen times throughout the growing and cropping season with allowed fungicides like sulphur or copper compounds; at these exposure levels they induce their own toxicity on plants.

The organic/conventional controversy has too often arisen in the past because there has been insufficient control of all the other major agronomic variables and they don’t progress beyond assaying phytochemical levels in the laboratory. Even the assays have been problematic as they may have lacked sensitivity or selectivity. Given there are thousands of these compounds in plants, each with their own chemical properties, bioaccessibility and bioavailability, metabolism, excretion, potency and efficacy properties, measuring pools of varying and unknown composition inevitably leads to confusion. Concentrations have also often been expressed in terms of wet weight which is highly variable. Nevertheless, these early studies would duly report that one system, organic or conventional, was better, equivalent or worse than the other. More sensitive and selective assay and extraction systems have since become more widely available (eg HPLC/mass spectrometry), allowing more concrete conclusions to be made regarding levels. However, merely recording the concentration of phytochemicals in a food is only a first step which should then be complemented with human studies to see whether recorded differences translate to different outcomes in the body. Does the particular food matrix of a given food compromise release and absorption of a phytochemical? Many of the reports in the literature have not done follow-on studies and so are incomplete, possibly misleading and can generate unnecessary controversy. The gold standard in biomedicine for questions of whether one practice or product is better, equivalent or worse than others in humans is the randomised double blind clinical trial, supported by competently conducted epidemiological, animal and laboratory studies.

The following study (European Journal of Nutrition (2010) 49, 301–310) illustrates this more thorough experimental design with sensitive and selective assays followed by clinical trials in healthy humans, with the conclusion that slight or zero differences in polyphenols between the two production systems do not follow through to differences in bioavailability, antioxidant status or immune parameters (peripheral blood mononuclear cell proliferation, cytokine secretion and natural killer cell activity).

Organic food sales have been increasing in recent years. It has been hypothesised that organically grown fruits are healthier based on their higher content of phytochemicals. However, data on the bioavailability of phytochemicals from organic- or conventionally produced plant foods are scarce. Two human intervention studies were performed to compare the bioavailability of polyphenols in healthy men after ingestion of apples from the different farming systems. The administered apples were grown organically and conventionally under defined conditions and characterised regarding their polyphenol content and antioxidant capacity. No significant differences in the polyphenol content and the antioxidant capacity from the organic and conventional farming system were observed. In the short-term intervention study, six men consumed either organically or conventionally produced apples in a randomized cross-over study. After intake of 1 kg apples, phloretin (Cmax 13 nmol/l, tmax 1.7 hr) and coumaric acid (Cmax 35 nmol/l, tmax 3.0 hr) plasma concentrations increased significantly in both intervention groups, without differences between the two farming systems. In the long term intervention study, 43 healthy volunteers consumed organically or conventionally produced apples (500 g/d for 4 wks) or no apples in a doubleblind, randomized intervention study. In this study, 24 hr after the last dosing regime, the apple intake did not result in increasing polyphenol concentrations in plasma and urine compared to the control group, suggesting no accumulation of apple polyphenols or degradation products in humans. Our study suggests that the two farming systems (organic and conventional) do not result in differences in the bioavailability of apple polyphenols.

A report in the journal Comprehensive Reviews in Food Science and Food Safety, (2010) 9, 270-277, entitled ‘A Review of the Nutrition Claims Made by Proponents of Organic Food’ states:

• The American Academy of Pediatrics and the American Medical Assn. have not supported the need for organic food.
• The Mayo Clinic and the American Dietetic Assn. state that there is no benefit from organic food.
• The U.S. Dept. of Agriculture states that there is no conclusion about the need for or benefit from organic food.
• After a thorough study of foods in the Government-funded Women, Infants and Children Program, the National  Academy of Sciences, Institute of Medicine made no reference to the need for organic food.

In addition:

• The US-based Institute of Food Technologists issued a Scientific Status Summary in 2006 stating: ‘While many  studies demonstrate qualitative differences between organic and conventional foods, it is premature to conclude that  either food system is superior to the other with respect to safety or nutritional composition. Pesticide residues,  naturally occurring toxins, nitrates, and polyphenolic compounds exert their health risks or benefits on a dose  related basis, and data do not yet exist to ascertain whether the differences in the levels of such chemicals between  organic foods and conventional foods are of biological significance.’
• A 2009 meta-analysis of the literature over the last 50 years found 52,471 relevant articles, and of 137 and 52  on crops and livestock resp, 55 were judged of satisfactory quality. It was concluded that: ‘On the basis of a systematic  review of studies of satisfactory quality, there is no evidence of a difference in nutrient quality between organically  and conventionally produced foodstuffs. The small differences in nutrient content detected are biologically plausible  and mostly relate to differences in production methods.’

Finally a few comments on some of the other drivers for those who eschew conventional foods. Use of synthetic pesticides and herbicides in conventional farming generally leads to higher levels in foods, even when government-mandated withholding periods are observed, and more than two thirds of organic food buyers will typically cite concern with increased levels as a reason for preferring organic. The important question is whether these remaining levels are relevant given what’s known of their toxicities? The WHO uses an ‘acceptable daily intake’ (ADI) as its minimal level of toxicological concern, and one US study of 285 foods found the presence of 38 pesticides at less than 1% of the ADI for 34 of them, with the other 4 being below 5%. To place this in perspective, the ADI typically represents a value 100 times lower than the highest level of pesticide exposure given to the most sensitive animal species throughout its lifetime that has not caused any toxicological effect.

A typical human exposure at 1% ADI represents an exposure 10000 times lower than levels that do not cause toxicity in animals. A separate and finite risk even in developed countries where compliance with toxicity regulations is periodically monitored, is the rogue grower who passes on product that has higher levels than legal. This occasionally happens in Australia from domestic produce and more often from imports, and deservedly receives much publicity and regulatory action. At least in growing your own you know what the fruit tree has or has not been exposed to. Taste is also frequently cited as being superior in organic foods by proponents. However, taste is such a subjective sense and varies so widely between individuals that it’s difficult to quantify reliably and objectively. For example, most people find pawpaw to be a very tasty fruit but for some it’s nauseating. Furthermore, when people are strong believers in the superiority of some product the placebo effect can be huge. As a result, support for equivalence, better or worse than the other production system is found in literature studies.

Organic farming relies on natural fertilisers, crop rotation, inter-row green manures, etc to build up soil fertility and supply necessary nutrients to plants. This may take some years to achieve, depending on how poor the soil is to start with. So early on in conversion to organic, yields may be greatly depressed but with good management may gradually approach the best conventional levels. Addition of these organic substances builds up soil organic matter and general fertility in a way that conventional practice does not. But then it relies on this build up to achieve its results whereas in the conventional approach nutrients are artificially added as and when needed. A further benefit of the organic approach in soils is that pathogen loads are commonly reduced due to increased competition from other microbes. You can find some commentary on the benefits of mulching/composting on soil properties in section II – Upgrading Our Gutless Sands. Another important consideration in the organic/conventional comparison is that in the latter, nutrients are applied when needed and plants can take up much of what’s required for the year. With organic fertilising, nutrient release (mineralisation) is less controlled and not timed to these periods, resulting in an increased proportion not being absorbed by the plants and being leached or volatilised.

In summary given the evidence to date for growers, the conventional approach can be made more sustainable and ecologically sound by adopting some traditional organic farming technologies and not rejecting all modern advances. For consumers, the case for some elements of organic rests not so much on superior nutrition, safety or taste but more on ecological, environmental and sustainability concerns. Viewing this question of organic vs conventional as exclusively either/or alternatives has and will increasingly need to be superseded with the more balanced integrated approach.